8.2.1.4 Application Curves

The DS160PR421 is a linear redriver that can be used to extend channel reach of a PCIe link. Normally, PCIe-

compliant TX and RX are equipt with signal-conditioning functions and can handle channel losses of up to 28 dB

at 8 GHz. In real implementation the channel reach is often lower. With the DS160PR421 in the link, the total

channel loss between a PCIe root complex and an end-point can be extended up to 42 dB at 8 GHz.

Figure 8-3 shows an electric link that models a single channel of a PCIe link and eye diagrams measured at

different locations along the link. The source that models a PCIe Transmitter sends a 16 Gbps PRBS-15 signal

with P7 presets. After a transmission channel with –30 dB at 8 GHz insertion loss, the eye diagram is fully

closed. The DS160PR421 with its CTLE set to the maximum (17 dB boost) together with the source TX

equalization compensates for the losses of the pre-channel (TL1) and opens the eye at the output of the device.

The post-channel (TL2) losses mandate the use of PCIe RX equalization functions such as CTLE and DFE that

are normally available in a PCIe-compliant receiver.

CPU / PCIe RC

16 Gbps, PRBS15

800mV

Pre-Cursor: 3.5 dB

Post-Cursor: -6 dB

DUT

PCIe 4.0 Redriver

RX EQ = 15 (17 dB)

TL1

-30 dB @ 8 GHz

TL2

-15 dB @ 8 GHz

PCIe

End Point

RX CTLE:

12 dB

Figure 8-3. PCIe 4.0 Link Reach Extension Using the DS160PR421

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DS160PR421

SNLS686 – FEBRUARY 2021

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